[ovirt-users] trouble when creating VM snapshots including memory

[Yaniv Kaul]

On Fri, Jun 9, 2017 at 3:39 PM, Matthias Leopold <
matthias.leopold at meduniwien.ac.at> wrote:

> hi,
>
> i'm having trouble creating VM snapshots that include memory in my oVirt
> 4.1 test environment. when i do this the VM gets paused and shortly
> (20-30s) afterwards i'm seeing messages in engine.log about both iSCSI
> storage domains (master storage domain and data storage where VM resides)
> experiencing high latency. this quickly worsens from the engines view: VM
> is unresponsive, Host is unresponsive, engine wants to fence the host
> (impossible because it's the only host in the test cluster). in the end
> there is an EngineException
>
> EngineException: org.ovirt.engine.core.vdsbroke
> r.vdsbroker.VDSNetworkException: VDSGenericException:
> VDSNetworkException: Message timeout which can be caused by communication
> issues (Failed with error VDS_NETWORK_ERROR and code 5022)
>
> the snapshot fails and is left in an inconsistent state. the situation has
> to be resolved manually with unlock_entity.sh and maybe lvm commands. this
> happened twice in exactly the same manner. VM snapshots without memory for
> this VM are not a problem.
>
> VM guest OS is CentOS7 installed from one of the ovirt-image-repository
> images. it has the oVirt guest agent running.
>
> what could be wrong?
>
> this is a test environment where lots of parameters aren't optimal but i
> never had problems like this before, nothing concerning network latency.
> iSCSI is on a FreeNAS box. CPU, RAM, ethernet (10GBit for storage) on all
> hosts involved (engine hosted externally, oVirt Node, storage) should be OK
> by far.
>

Are you sure iSCSI traffic is going over the 10gb interfaces?
If it doesn't, it might choke the mgmt interface.
Regardless, how is the performance of the storage? I don't expect it to
require too much, but saving the memory might require some storage
performance. Perhaps there's a bottleneck there?
Y.


>
> it looks like some obvious configuration botch or performance bottleneck
> to me. can it be linked to the network roles (management and migration
> network are on a 1 GBit link)?
>
> i'm still new to this, not a lot of KVM experience, too. maybe someone
> recognizes the culprit...
>
> thx
> matthias
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